a) Field of the Invention
The invention is directed to an arrangement for fixing components of an optical system such as lenses, mounting rings, spacers, and the like which are enclosed by a common tube in which they are guided radially and held in the axial direction under pretensioning in an elastic manner.
b) Description of the Related Art
It is conventional in optical engineering to compensate for thermally induced changes in length of structural component parts within an optical system and deviations in length occurring during manufacture by means of resilient holders with pretensioning in the direction of the optical axis. When the parts are arranged successively axially, a first part generally rests on a fixed support. In the case of the final structural component part, a functional part, e.g., a rubber ring, which is pretensioned in a springing-elastic manner extends over the edge area and fixes the parts in position.
A suggestion of this kind is disclosed in DE OS 29 22 287. In this case, the resilient holder in a mounting for optical lenses is characterized in that a ring of rubber-like material is arranged in an annular groove in the mounting body. The annular groove is partially covered in the axial direction by the circumferential surface of the lens. The space provided for the ring between the lens and mounting body is widened outward. The lens is held as an individual part between a fixed annular stop, which is formed integral with the mounting body, and the rubber ring. For this purpose, the pretensioning force exerted by the elastically deformed rubber ring is transmitted to the mounting body by the annular stop on the one hand and by the contact surface of the rubber ring on the other hand. It is disadvantageous that this solution compensates for changes in length and differences in length only for one structural component part, namely the lens. A further disadvantage consists in that a change in the magnitude of the pretensioning force in defined steps, as is desirable for special optical systems, is not possible in this holder because the position of the rubber ring is permanently fixed by the position of the groove. When no groove is provided (in the case of a frictional connection with the mounting body), the pretensioning force is dependent in any case on the friction between the rubber and the cylindrical wall of the mounting body, which friction is influenced by numerous factors, and consequently can not be changed in a definite manner.
DE OS 23 62 041 describes a mounting in which a lens or lens group is held in its mounting by means of a ring which can be screwed in. The ring has elastic projections which serve as a support for the lens group and hold the latter under elastic pretensioning. In this case, while the magnitude of the pretensioning force can be varied by the depth to which the ring is screwed in, it is disadvantageous that the thread is uneconomical to manufacture and the assembly of the optical system is time-consuming.
Another solution for the elastic support of optical lenses in their mountings is disclosed by DE OS 28 46 241. At least two small plates of resilient material, e.g., metal, which engage over the edge area of the lens are provided at the side of the lens located opposite from the fixed support and are connected in a positive engagement with the mounting, wherein they contact the lens under pretensioning. The springing plates are simply inserted into corresponding openings in the mounting during assembly. This proposal for elastic axial support is likewise disadvantageous in that a defined increase or decrease in the pretensioning force in defined steps is not possible because the position of the small plates is permanently determined in the axial direction by the openings in the mounting.